Therapeutic benefits can be achieved in some instances by providing an active agent to a subject in a manner that extends the time over which the active agent is released. Further, therapeutic benefits can be achieved by providing an active agent to a specific target tissue, instead of systemically. This is because the effect of the agent on the target tissue can be maximized while limiting side effects on other tissues. One approach to providing these benefits is to use a coating system containing an active agent on a medical device.
The specific rate at which an active agent is eluted from a coating or material is of importance. If the active agent elutes too quickly, there may be too much of an active agent that is dosed to a particular tissue. Over-dosing of an active agent may have harmful side effects. If the active agent elutes too slowly, there may be too little of an active agent that is dosed to a particular tissue. Under-dosing of an active agent may fail to yield a therapeutic effect.
A desirable elution rate for one active agent may be different than a desirable elution rate for another active agent. Further, a desirable elution rate for a particular active agent may vary with the particular type of condition being treated.
Therefore, a need exists for coatings, coating systems, and coating methods that achieve a predetermined rate of elution of an active agent from a coating or material.